1. FIELD OF THE INVENTION
This invention relates to photographic elements and more particularly to photographic elements having a light-sensitive silver halide layer and a transparent magnetic recording layer.
2. DESCRIPTION OF RELATED ART It is known from various U.S. patents, including: U.S. Pat. Nos. 3,782,947; 4,279,945; 4,990,276; 5,217,804; 5,147,768; 5,229,259, and others; to include in a light-sensitive silver halide photographic element a transparent magnetic recording layer. Such elements are advantageous because they can be employed to record images by the customary photographic process while at the same time information can be recorded into and read from the magnetic recording layer by the techniques similar to that employed in the magnetic recording art.
A difficulty, however, arises in that magnetic recording layers generally employed in the magnetic recording industry are opaque, not only because of the nature of the magnetic particles, but also because of the requirements that the recording layer contains other additives which further create problems with regard to the optical characteristics of the layer. Also, the requirements of recording and reading of the magnetic signal from a transparent magnetic layer present on a photographic element are more stringent than that found in conventional magnetic recording because of the loading of the magnetic particles in the transparent magnetic layer and the nature of the photographic element.
Thus, the presence of the magnetic recording layer cannot interfere with the primary function of the photographic element which is to achieve realistic reproductions of the original image. In addition, the magnetic recording layer must be capable of accurately recording the information applied thereto and reading out the information on demand. This is particularly difficult because the loading of the magnetic particles in the transparent layer must be such as to not interfere with the quality of the photographic elements.
Finally, the photographic element and particularly the transparent magnetic recording layer provided thereon must be capable of repeated use in both the recording and reading mode and, therefore, must have improved running, durability, head cleaning properties and not adversely affect the quality of the photographic element. For example, during the residence of the film in a camera, entries may be made to the magnetic recording layer for every exposure, and an indeterminate number of read operations are conducted depending on the particular application to which the film is used. This also is true in the processing of the film and in subsequent use of the processed film for additional copies, enlargements and the like.
It can, therefore, be readily seen that it would be highly desirable to provide photographic elements having a transparent magnetic recording layer exhibiting improved magnetic and photographic performance as well as improved running durability and head cleaning properties. This goal is extremely difficult to achieve because of the nature and concentration of the magnetic particles required to provide sufficient signal to write and read magnetically stored data, the effect of any noticeable color, haze, or grain associated with the magnetic layer on the photographic layers and the effect of the magnetic layer on the optical density and granularity of the photographic layers. Thus, all of these various characteristics must be considered both independently and cumulatively in order to arrive at a commercially viable photographic element containing a transparent magnetic recording layer that will withstand repeated and numerous passages through the recording and reading zones of a suitable apparatus. Also, because of the curl of the element, primarily due to the photographic layers and core set, the film must be held tightly against the magnetic heads by pressures much higher than those in conventional magnetic recording in order to maintain film plane flatness in the recording and reading zone.